I would highly recommend the Panasonic Leica 25mm f1.4 lens, at around $600 it is considered on the sharpest and best performing lenses made for ANY system.
Another must have lens is the Olympus 45mm f1.8, amazing image quality, around $400.
Wide angle lens would be the Panasonic 14mm f2.5. a bargain lens.
The above 3 mentioned lens are considered "fast lenses" in that the Aperture (especially the f1.4 and f1.8) opens very wide allowing for faster shutter speeds, nice blurred backgrounds and the ability to shoot in lower light situations without the flash. I shoot with a GH1 and have had great results. I would also recommend Adobe Lightroom to process and catalog your photos. Adobe has amazing video tutorials at Adobe TV.com.
I also recommend shooting in "A" aperture mode with the above mentioned lenses so you can have the most control of the getting the most out of those nice wide apertures. Have fun!